package org.newdawn.slick.state.transition;

import org.newdawn.slick.Color;
import org.newdawn.slick.GameContainer;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.state.GameState;
import org.newdawn.slick.state.StateBasedGame;

/**
 * A transition to fade out to a given colour after a delay.
 *
 * @author kevin (base)
 */
public class DelayedFadeOutTransition implements Transition {
    /**
     * The color to fade to
     */
    private final Color color;
    /**
     * The time it takes the fade to happen
     */
    private final int fadeTime;
    /**
     * The time it takes before the fade starts
     */
    private final int delay;
    /**
     * The elapsed time
     */
    private int elapsedTime = 0;

    /**
     * Create a new delayed fade out transition.
     */
    public DelayedFadeOutTransition() {
        this(Color.black, 500, 0);
    }

    /**
     * Create a new delayed fade out transition.
     *
     * @param color The color we're going to fade out to
     */
    public DelayedFadeOutTransition(Color color) {
        this(color, 500, 0);
    }

    /**
     * Create a new delayed fade out transition
     *
     * @param color    The color we're going to fade out to
     * @param fadeTime The time it takes the fade to occur
     * @param delay    The time before the fade starts (must be less than {@code fadeTime})
     * @throws IllegalArgumentException if {@code delay} is greater than {@code fadeTime}
     */
    public DelayedFadeOutTransition(Color color, int fadeTime, int delay) {
        if (delay > fadeTime)
            throw new IllegalArgumentException();

        this.color = new Color(color);
        this.color.a = 0;
        this.fadeTime = fadeTime;
        this.delay = delay;
    }

    @Override
    public boolean isComplete() {
        return (color.a >= 1);
    }

    @Override
    public void postRender(StateBasedGame game, GameContainer container, Graphics g) {
        Color old = g.getColor();
        g.setColor(color);
        g.fillRect(0, 0, container.getWidth() * 2, container.getHeight() * 2);
        g.setColor(old);
    }

    @Override
    public void update(StateBasedGame game, GameContainer container, int delta) {
        if (elapsedTime < delay) {
            elapsedTime += delta;
            return;
        }

        color.a += delta * (1.0f / (fadeTime - delay));
        if (color.a > 1)
            color.a = 1;
    }

    @Override
    public void preRender(StateBasedGame game, GameContainer container, Graphics g) {
    }

    @Override
    public void init(GameState firstState, GameState secondState) {
    }
}
